Nuno,
I've heard complaints about the Alexa and F35. The F35 ones are about resolution, sensitivity and DR (esp. when compared to more modern cameras). Not that the camera doesn't take lovely pictures, b/c it certainly does. With the Alexa, I'm sorry but I'm not a liberty to say as it was a private conversation that I had with a friend. But these complaints are image related and not insignificant under certain circumstances.
I also heard some hushed criticisms of the C300 image by a few folks while at the Paramount event, but when you're invited to a wedding, you generally say that the bride looks lovely.
I'm sorry but a private conversation with your buddy, means nothing, and if the folks at Paramount wanted to speak up, or if the issues they saw were that alarming, well, blogging should have been a nice way to let us know about it, but nothing sufficed. So, nothing to complain about, yet.